Protective device

ABSTRACT

A protective device having a shell structure and being shaped from a plate-shaped material, in particular but not exclusively, adapted for covering of a sub sea structure, such as at least one pipe line ( 21, 22 ), a Christmas tree or parts of such constructions. The protective device is designed as a downward open and upwards closed convex container or channel, comprising a substantially plane roof plate ( 5 ), e.g., two substantially plane and inclined side walls ( 3, 4 ) which may end in an individual foot plate ( 1, 2 ). The protective device or parts thereof is (are) designed with a shallow wave structure or with a weakly corrugated structure, the waves having a wave length ( 1 ) above 2.5 times the wave-height (h), and where the wave height does not exceed 10 times the thickness (d) of the plate-shaped material. As examples of usages the following may be mentioned: protection of constructions on land, lining of tunnels, building materials and modules for offshore living quarters.

The present invention relates to a protective device made from aplate-shaped material, and relates in particular to a shell-shapeddevice adapted to cover a sub sea construction or parts of such aconstruction on the sea bed, which protective device is shaped as adownwards open and upwards closed convex shell, comprising asubstantially plane roof plate with at least one mainly flat andpreferably oblique directed side wall, which preferably ends in atransverse foot plate.

The device has extremely good mechanical qualities and low-weight andmay accordingly be used for many different applications, such as tunnellinings, modules for buildings or building elements.

Previously there are known different protective devices adapted forcovering of structures and equipment on the sea bed, to protect suchstructures against damages caused by over trawling, anchoring or othermechanical strain situations from ships and similar activities in theocean, above the sub sea structures.

As examples of such protective devices it may be referred to NorwegianPatent No. 139.790 describing a device for protection of structures onthe sea bed, where the protective device is a reinforced concreteelement comprising two interconnected reinforcement nets. Further it isreferred to Norwegian Patent No. 144.834 in which a similar protectivedevice is built up as a covering, among other comprising flexibleinterconnected concrete elements, linked together both crosswise andlengthwise, and also UK-patent application No. GB 2178127A, whichrelates to a method for manufacturing of a protective mat for a flexiblepipe, and where the mat elements are provided with pairs of holesdesigned to receive interlinking ropes or similar elements.

The above-mentioned solutions are all encumbered with differentdisadvantages, e.g. they are very heavy and compact, and accordinglylarge and also expensive vessels are required to produce/deploy/mountthe earlier known protective devices, and the vessels also have toundertake many journeys before a long pipeline has been covered, causinglarge costs and risks during laying.

It is also previously known to make protective covers for sub sea usefrom plastics, and then in particular laminated, multi layer materials.The advantages are a low weight and less expensive materials, but thesesolutions have also led to problems, in particular as the material mustbe relatively thick to obtain sufficient stiffness and pressureresistance, but all the same large protective constructions built up oflaminated artificial compositions, will easily be twisted so that thestructures are unstable both during manufacturing, transportation andalso during deployment on the site.

The object of the present invention is to provide a protective device inparticular adapted for covering of a sub sea construction, such as apipeline, a Christmas tree etc. in a much less expensive way and atleast just as efficient as earlier solutions. Further it is an object ofthe present invention to provide a stable protective device which is notexpensive, which is corrosion and pressure resistant, has a low weightcausing that many or very large protective devices may be transported bya ship, which devices all the same are more stable than previously knownlightweight constructions of similar design.

The object is also to provide a protective device for many applicationsboth on land and in marine environments, which device is many cases maybe used as a separate element and in other connections may be used as amodule together with cooperating and similar, but not necessarilyidentical modules.

These objects are met by a protective device according to the belowclaims. The idea may primarily be said to stiffen the protective deviceas parts of it or the complete device is given a shallow wave form or aweakly corrugated shape which results in a rigid design without acorresponding weakening on the element.

It should be mentioned that corrugations also earlier have been used fordifferent protective devices, but then as deep corrugations causing avery stiff material, e.g. in radial direction for corrugated tubes, butat the same time with increased flexibility or in other words increasedweakening against bending stress, acting longitudinal to these deepcorrugations. The measure of the present invention may accordingly besaid to find an optimal value of shallow or weak corrugations so thatincreased stiffness is obtained across to the corrugations without apronounced reduction of the rigidity longitudinal to the corrugations

If only one portion of the protective device, e.g. the roof plate of thesame, is provided with shallow corrugations according to this invention,the interaction between these corrugations and the adjacent walls with acertain angle to the roof plate, causes a further stiffening of thedevice. This is in particular the case when the side walls are arrangedacross to the corrugations and is integrated with the roof plate in onesingle unit.

To give a clearer and more unambiguous understanding of the invention itis referred to the more detailed description below, and to theaccompanying drawings in which:

FIG. 1 illustrates a protective device according to one embodiment ofthe present invention,

FIG. 2 illustrates the protective device according to FIG. 1, however insome more detail,

FIG. 3 shows an example of a preferred wave design, and

FIG. 4 shows a local protective device having a main structure similarto a bucket or box, turned upside down.

It is pointed out that the same reference numbers are used, where foundappropriate, when referring to corresponding details in the figures,that minor details note required to understand the invention may beomitted in the drawings to avoid crowding of the same, and that thedifferent figures or parts of figures not necessarily are in same scale.The scale used longitudinally to and across to the material are also notnecessarily identical.

In FIG. 1 the protective device according to the present invention isshown, in which the protective device consists of a longitudinal,tunnel-shaped construction, comprising two foot plates 1 and 2preferably in the same plane, two more or less inclining side walls 3, 4which may be plain or longitudinally corrugated related to the length ofthe device, and a roof plate 5 which on the figure is shown corrugatedby shallow corrugations along the extension of the device. In a similarmanner it is on FIG. 1 assumed that the foot plates 1, 2 are arranged onthe sea bed 9, that the protective device extends above longitudinalelements which are to be protected, such as the pipelines 21, 22, and atthe same time the foot plates 1, 2 and portions of the remainingprotective device may be partly or completely covered by backfillmaterial 6 to stabilize and to anchor the protective device in correctposition on the sea bed 9.

It should be mentioned that the protective device may be built insections of substantial length or may be produced in short sections,preferably sections having a length 10 at least corresponding to onecomplete corrugated wave periode. In addition the protective device ofcourse may be provided with branches or may include specific jointswhich may be of Y-shape, L-shape, X-shape, or T-shape when seen fromabove.

FIG. 2 shows in more detail how the bent portions between the plate 1,the side wall 3 and the roof plate 5, respectively, are designed in apreferred embodiment. It is assumed that the corners are rounded andtheir curve radius may preferably be in the range 50-400 mm, whichhowever, do not represent absolute limits. However, rather abruptdirectional changes are preferred, without sharp corners, as this isdeemed to give the best mechanical qualities. Again it is pointed outthat the wave structure in the roof plate 5 gives a powerful stiffeningof the channel in its crosswise direction, while the interaction betweenthe roof plate 5 and the side walls 3, 4 will lead to substantialstiffening of the device in its longitudinal directions, i.e. across allthe corrugations, in particular when the channel is built up from onesingle plate element.

In FIG. 3 there is shown a cross section through the material of theroof plate 5, taken along the plane III—III in FIG. 2. However, theplate thickness is strongly exaggerated to make the figure more clear.As assumed the protective device may be produced from a multi layerartificial material preferably comprising two outer laminated layers 31,32 made up from a high impact, fibre reinforced material and a centrallayer 30 of plastics, preferably made of a high density-polyethylenewhich endures the pressure conditions on large ocean depths. As shown onall figures at least the roof plate 5 is provided with longitudinal,shallow corrugations, such that the wave-length 10 of one corrugation is1, the wave-height of one corrugation is h and finally the totalmaterial thickness of the plate material is d.

To explain the idea of said invention in a simple way, it may be saidthat if the roof plate 5 had been designed with deep corrugations sothat the cross section was more similar to the cross section of usualcorrugated iron and similar products, the stiffness in the longitudinaldirection would be reduced while the stiffness in the vertical planewould increase considerably. By using shallow corrugations having a lowbow related to the thickness of the material and related to thewavelength of the corrugations, a considerable increase in crosswisestiffness is obtained without a reduction of the stiffness longitudinalto the tunnel, worth mentioning. Practical tests have shown that theoptimal conditions are obtained when the wavelength is at least fivetimes the bow. On the figure it is assumed that the wavelength is 10times the waveheight, measured from the apex of the laminate. Thethickness of the material is however shown exaggerated so that thelayers will be clearly shown on the figure. When the production isconsidered, it is also considered advantageous which shallowcorrugations which much easier may be combined with the integratedlinking to the side walls.

Tunnel sections built in this manner will, according to practicaltesting, obtain a very high stiffness even if the thickness of the platematerial is reduced from previously used values; the sections are stableduring transportation and handling; the deployment may take place muchfaster and the material costs are considerably reduced. It is alsoassumed that the shape including longitudinal curved zones with radii rand R on FIG. 2, contributes to obtaining a rigid tunnel which is stablein its longitudinal direction.

On FIG. 4 a corresponding protective device having the shape of a box orbucket turned upside down, is shown. Here the tunnel is closed by endwalls 23, 24 which also are integrated with the remaining parts of thedevice. This unit may have the shape of a box as shown on FIG. 4, or itmay be more or less conical. If the shape is that of a truncated cone,or a bucket turned upside down, the bottom pointing upwards, may have ashallow wave form to stiffen the construction.

When the stability of the construction is considered, it may be takeninto account that the dimensions of the device may be very large, forinstance several tens of metres, while the thickness of the materialshould be as small as possible, may be a few centimetres. The material,the weight and the time used for assembling, are reduced as increasedstiffness and stability allow a lower total weight giving the samedegree of protection.

By alternative solutions also other parts of the device or the tunnelmay be corrugated, but in most cases it will be desirable that at leastthe roof plates 5 are corrugated. When the cross section of the platematerial is considered, this may advantageously show a laminatedstructure as in FIG. 3, and then preferably a so-called sandwichmaterial as specified in the Norwegian printed patent publication No.175.911 from the same applicant.

It is assumed advantageous, especially when used below water, that thefoot plates 1,2 have a higher relative weight than the remaining partsof the protective device, or that the foot plates in one manner oranother are provided with additional weight so that the tunnel willobtain a correct orientation when lowered in water.

As assumed on FIG. 1 the tunnel may be divided in short sections,preferably having a length quite down towards the wave length of thecorrugations. Each section may be arranged abutting, or with someoverlap, and in the latter case the end portion of each section may bedesigned for such overlapping.

The side walls or the end walls of the device may be provided withsuitable recesses to receive pipelines, cables etc.

Even if the invention above is described as a protection device, and itsubstantially is to be used as such and then in particular below water,this should not be considered as a limitation for such applicationsonly. Important qualities of the device are low weight, high strength,high stiffness, a very high resistance against corrugation, and thedevice also is weather and water resistant. Accordingly it should beclear for everyone that the device also may be used on land, anddependant of the design and dimensions the device may, e.g. be used forprotection of structures on land, internal lining and reinforcing of allkind of tunnels, modules in building techniques, and protective coveringof different objects such as transportations devices of all kinds; fromhigh velocity trains to space stations. The device may also, whenmanufactured with large dimensions, be used as living quarters, forinstance in offshore platforms, or as a carport. And when produced withsmall dimensions it may replace brics or concrete blocs, especially whena low weight load is preferable. It should also be pointed out that theangles between the different parts of the device, such as the anglesbetween the roof plate and the respective side walls, and also betweenthe side walls and their associated foot plates, may be varied freely,dependant of the use, and also of the relative dimensions between roofwidth, height of side walls and width of foot plates. Produced with alarge width combined with very short side walls, the element may also beused as a floor board or floor construction with stiffening side wallshaving so low a height that they only acts as side edges of the floor.In a similar manner the foot plates may just as well point inwards, i.e.turn below the floor plate, as point outwards.

What is claimed is:
 1. A protective device made from a plate-shapedmaterial and shaped as a downwards open and upwards closed convex shellconstruction, comprising as integrated portions: a roof plate; and atleast one side wall which ends in a footplate, wherein the roof plate isundulate so as to stiffen the protective device, with cursive waveshaving a longer wave length than 2.5 times the wave height (h), andwherein the wave height does not exceed ten times the thickness (d) ofthe plate-shaped material, and where the roof plate is integrated withthe at least one side wall.
 2. A protective device as claimed in claim1, wherein the wave length is less than 25 times the wave height (h). 3.A protective device as claimed in claim 1, wherein said at least oneside wall of the protective device is undulate.
 4. A protective deviceas claimed in claim 1, wherein the foot plate is undulate.
 5. Aprotective device as claimed in claim 1, produced from a plate-shaped,multi layer, laminated material.
 6. A protective device as claimed inclaim 5, made of a laminated, artificial material.
 7. A protectivedevices as claimed in claim 6, wherein the laminated artificial materialcomprises at least three layers, at least one layer being an artificialmaterial having a large impact resistance.
 8. A protective device asclaimed in claim 1, assembled from a plurality of longitudinallycombined sections.
 9. A protective device as claimed in claim 8, whereineach section has a length at least corresponding to one wave-length. 10.A protective device as claimed in claim 1, wherein the foot plate ismanufactured from a material having a density higher than density of theremaining parts of the protective device, and density of the completedevice is higher than density of water.
 11. A protective device asclaimed in claim 1, further comprising undulate end walls.
 12. Aprotective device as claimed in claim 1, wherein the wave length is morethan six times the wave height and less than ten times the wave height.